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// Copyright 2012 Google, Inc. All rights reserved.
//
// Use of this source code is governed by a BSD-style license
// that can be found in the LICENSE file in the root of the source
// tree.
package layers
import (
"encoding/binary"
"fmt"
"github.com/google/gopacket"
)
// Loopback contains the header for loopback encapsulation. This header is
// used by both BSD and OpenBSD style loopback decoding (pcap's DLT_NULL
// and DLT_LOOP, respectively).
type Loopback struct {
BaseLayer
Family ProtocolFamily
}
// LayerType returns LayerTypeLoopback.
func (l *Loopback) LayerType() gopacket.LayerType { return LayerTypeLoopback }
func decodeLoopback(data []byte, p gopacket.PacketBuilder) error {
// The protocol could be either big-endian or little-endian, we're
// not sure. But we're PRETTY sure that the value is less than
// 256, so we can check the first two bytes.
var prot uint32
if data[0] == 0 && data[1] == 0 {
prot = binary.BigEndian.Uint32(data[:4])
} else {
prot = binary.LittleEndian.Uint32(data[:4])
}
if prot > 0xFF {
return fmt.Errorf("Invalid loopback protocol %q", data[:4])
}
l := &Loopback{
BaseLayer: BaseLayer{data[:4], data[4:]},
Family: ProtocolFamily(prot),
}
p.AddLayer(l)
return p.NextDecoder(l.Family)
}
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